Late 260Z Smog Pump adjusting arm

[Captain Obvious]

Haha! Getting confident is just an invitation to let Murphy refresh you on his laws. And the cockier you get, the more expensive he gets. 

Patcon, It's still gets "cold" sometimes in FL. Heck... I could say the same thing about where you are compared to PA. 

[tunesnxs]

Patcon,

     yep, I'm in Orlando, and yes it gets cold here!!!! This winter it got down to the low 60's!!!! We all thought the end was surely near!

Capt. Obvious,

     I did the ten second shake test last night, and sure enough it spat on me. So after seeing that I am convinced. I took the thermostat valve off the water line coming from the rear carb and did the heat test. I slowly heated it up with a torch and eventually the valve mostly closed, but long after I think it should have. I cooled it off in a bucket of water (PSSSSsssssss) and then let it soak in a bucket of CLR. It did look rather rusty inside the valve, so tonight I'll remove it and let it soak a few hours in some OSPHO to remove all the rust internally. If it doesn't begin to operate correctly after that, I'll just block it up with something semi permanent.

[Captain Obvious]

Excellent. Sounds like my skepticism was unfounded and I hope that you have identified the root cause. There has been chatter about that thermostatic valve in the past, but I'm not aware of a cheap viable alternative. I hope yours cleans up with the dunking, and if not, it sounds like you're going to have to just remove the carb water flow like so many 260 owners before you.

Wow... Down to the 60's. Everyone wearing winter coats? 

[Captain Obvious]

So something else you mentioned before... You said that the water passage going to the balance tube was clogged. That passage to the balance tube is primarily to cool the EGR valve and the balance tube where the EGR mounts. If your EGR system is functional, it get's extra hot there and I've seen reports of the passageways burning through due to the heat. Point is... If your EGR is working, you might want to make sure that line flows.

Also, it's a good idea to keep some small amount of coolant flow into the thermostat housing, even when the engine is cool. Thoughts being, you don't want a stagnant pool over by the thermostat. In the stock configuration, you've got three ways for water to flow through the intake tract: 1) through the carbs, 2) through the balance tube, 3) through the intake manifolds. I don't remember if all of those three paths are regulated by the thermostatic valve, but if you do block off that valve, it might be a good idea to make sure at least on of those three paths still passes water somehow.

[tunesnxs]

8 minutes ago, Captain Obvious said:

Wow... Down to the 60's. Everyone wearing winter coats? 

Oh yeah! it's funny, when the temp gets up to 40 in Alaska, everybody is out in shorts and t-shirts. When the temp gets down to 70 in Florida, everybody has their "Nanook of the North" jackets on!

 

And yes, the only water that goes through that valve is from the carbs, so the other two sources are still there and functioning. (I made sure they were still clear last night) So, if I end up blocking that valve passage, there will still be water flowing through the balance tube and manifolds.

[Captain Obvious]

Excellent. So make sure you keep us posted on the original problem and what the behavior is after you figure out what you're going to do about that thermostatic valve. This would be the first well documented case I've been close to.

[Patcon]

22 hours ago, Captain Obvious said:

Haha! Getting confident is just an invitation to let Murphy refresh you on his laws. And the cockier you get, the more expensive he gets. 

Patcon, It's still gets "cold" sometimes in FL. Heck... I could say the same thing about where you are compared to PA. 

I understand, it's all perspective. I looked up Orlando avg temps their lowest is 49 in January. Their lowest tend to be in the 60's I would think carb heaters would be unneeded in those temps...balmy compared to PA

[tunesnxs]

Ok guys and gals, Here is what I did and discovered.

I took the "thermostatic valve" off and soaked it in CLR for about 24 hours. It still looked a little rusty in there so I soaked it in some OSPHO for another 24 hours. After that I boiled it in some hot water with a hose attached to it. According to the candy thermometer in the pot with the valve, it closed at about 195 to 200º I thought that a bit too high, but I installed it anyway. After driving around the block a couple of times, it was obvious that the problem was not remedied. I then thought, “why not? I’ll just go ahead and block it up and see what that gets me”. So I put a plug into the hose right before the thermostatic valve. Well, I have not been able to create the problem since!

I took a drive at noon down Country Club Rd. (what a great drive for the Z) and not one sputter!!!! I even turned the AC on for the way back just to tax the most out of the engine, and it purred like a kitten!!!

So, after all this, I am convinced, the water flowing through the carbs was, plain and simple, just a bad design! Maybe if that water originated post radiator, and not post engine block it might make a little difference.

Edited May 15, 2016 by tunesnxs

[Captain Obvious]

Great results. Glad you could come up with a solution to your issues.

 

I wouldn't necessarily call the water flowing through the carbs a bad idea though. It speeds warm-up and improves performance in areas of the world that are not as hot as where you are. It also prevents icing which could occur even where you are. It's just clear that "too much of a good thing" can cause problems.

 

If your valve isn't closing until 195-200, then that's too high. Test procedure on 74 FSM page ET-5 says is should be closing around 130F.

In your climate, I suspect 130F occurs about thirty seconds after leaving your house. Point is, blocking it off completely isn't much of a change where you live!  

[tunesnxs]

I did search the ol inter-web for a replacement valve, but it seems they simply do not exist in "new" condition.

[Captain Obvious]

I believe there are options available for a replacement thermostatic valve, but it won't be a direct drop in. There are valves for other applications (not necessarily specifically automotive) out there if you want the function and are willing to deal with having to modify the system to adapt a different form factor.

Here's a couple ideas:

Heat activated trap
http://www.thermomegatech.com/product/hat/

Hot water balancing valve:
http://www.thermomegatech.com/product-categories/domestic-hot-water-balancing/

There has also been some past discussion at the Z car forums. Here, Zcar, and Hybrid. Search isn't the best at any of them, but if you've got the time...